After making his directorial debut with the totally distasteful and juvenile found footage comedy, “Project X,” it wouldn’t have been surprising if Nima Nourizadeh never worked in Hollywood again. But someone clearly saw something in the filmmaker that warranted giving him another chance, and while he doesn’t exactly redeem himself with the action-comedy “American Ultra,” it does prove that he’s at least somewhat competent behind the camera. That’s hardly a ringing endorsement, and deservedly so, because although the movie boasts a talented cast and intriguing premise, it never amounts to more than a mildly amusing end-of-summer distraction that squanders its considerable potential under the indecisive direction of Nourizadeh.

Jesse Eisenberg stars as Mike Howell, an unambitious stoner who’s perfectly content with his mundane life in West Virginia alongside his live-in girlfriend, Phoebe (Kristen Stewart). Mike is completely in love with her, and even plans a romantic getaway to trip in order to propose, but for some reason, he keeps having panic attacks that prevent him from leaving town. Unbeknownst to him, his crippling anxiety is actually a side effect from an experimental government program he volunteered for that wiped his memory and turned him into a CIA sleeper agent. When the program’s architect, Victoria Lasseter (Connie Britton), learns that bureaucratic brownnoser Adrian Yates (Topher Grace) plans to terminate all the subjects from the abandoned project, she decides to activate Mike using a secret code phrase and give him a fair shot at survival. But it doesn’t work as expected – that is, until Yates sends a pair of assassins to kill Mike and he snaps out of his daze, dispatching them with only a spoon and a cup of ramen. Marked for death and forced to go on the run, Mike must utilize his new abilities to rescue Phoebe when she’s kidnapped by Yates and his team of programmed killers.

A high-concept movie that’s equal parts “Pineapple Express” and “The Bourne Identity,” “American Ultra” attempts to strike a balance between the pot-driven humor of the former and the super-spy action of the latter, but ends up as a bit of a tonal mess in the process. The film works in fits and starts, but it never really finds its groove; for every great moment or idea, there are two more that fall flat. Furthermore, while Nourizadeh’s action sequences are energetic and well-shot, they’re so ultraviolent that it becomes gradually more disturbing with each kill, which are played less for cartoonish laughs than gory realism. There was definitely an opportunity for some biting commentary on the irony of the U.S. government turning a stoner into a stone-cold killer amidst its War on Drugs, but sadly, “American Ultra” doesn’t seem interested in that kind of satire.

Writer Max Landis does have some fun playing with genre conventions in the same way that he did with superhero thriller “Chronicle,” but it’s not as effective here, perhaps lost in translation from page to screen. Thankfully, Eisenberg and Stewart have such great chemistry (picking up right where they left off with 2009’s “Adventureland”) that it saves the movie from being a complete disappointment. Not only do they handle the comedy and action beats with aplomb, but the pair adds an unexpected sweetness to their characters’ romance that you don’t normally find in this type of movie. The supporting cast doesn’t fare nearly as well, however, mostly because Nourizadeh doesn’t seem to know what to do with them. Britton and Grace are terribly miscast as the dueling CIA agents (the latter, in particular, is too over-the-top without ever posing a legitimate threat), while Tony Hale, Walton Goggins and John Leguizamo are all wasted in minor supporting roles.

When it focuses on Mike and Phoebe’s relationship, the movie is actually quite enjoyable, but it’s constantly being undermined by the dopey CIA subplot. The story is also pretty generic for a film that had the creative license to explore new territory, and it’s hard not to blame Nourizadeh for these shortcomings. “American Ultra” was never aiming to be high art – not even in the pharmaceutical sense – but just because it encourages you to turn off your brain doesn’t give it the excuse to be lazy. Though the movie will likely find an audience among the college crowd during late-night showings on cable TV, “American Ultra” had the makings of something much more ambitious. What we got instead was this half-baked pot brownie of an action-comedy, which gives you just enough of a buzz to make you wonder what it could have been in the hands of a more assured filmmaker.